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Dr. Jean-Francois Bisson of University of Moncton will be presenting at this week's physics colloquium. Please join the presentation on Thursday, March 31st at 4:00pm via Zoom.
Exceptional Points in the Polarization Space with Anisotropic Materials
The polarization state of light continuously changes as it propagates inside an anisotropic material, but there exist a pair of special polarization states, called eigenstates, which remain unaffected. These eigenstates are often mutually orthogonal but for anisotropic materials with both birefringence and diattenuation, this may no longer be the case. Such materials may even display singular axes, which are propagation directions where the two eigenstates coalesce into a single eigenstate. It is possible to create such behavior, called exceptional points (EPs), with specially engineered thin films. Glancing angle deposition (GLAD) is a thin-film deposition technique that lends itself to the creation of anisotropic thin films. It allows one to control the film’s optical properties by engineering the porosity at the nanoscale. This produces a metamaterial with quite unique properties that differ from those of the bulk material. Recently, we demonstrated the existence of EPs in helically structured thin films made by GLAD. EPs show enhanced sensitivity to a perturbation compared to a conventional sensor. However, for a passive device, the realization of such device is quite challenging because the enhanced sensitivity to a perturbation requires one to continuously adjust the input polarization state so that it remains an eigenstate. It is possible to overcome this issue by using active devices such as a laser oscillator, whose output beam is fundamentally a polarization eigenstate of the resonator. I will show that properly engineered anisotropic laser mirrors can not only eliminate the dual polarization emission at an EP but also suppress other competing modes to create emission at a single frequency.
Biography: Jean-François Bisson was born in Montreal, Canada. He received his undergraduate and Master’s degrees in engineering physics from École Polytechnique de Montréal and a doctorate degree in Physics from Université Pierre et Marie Curie in France, in 1999. After his doctorate, he joined the National Research Council of Canada, where he developed optical sensors for the control of the industrial coating deposition processes. In 2002, he joined the Institute for Laser Science in Tokyo, Japan, for developing ultra-transparent optical laser ceramics, a novel class of materials used to make high-power lasers. In 2007, he joined Amada Corp. for the development of a 4-kW fiber laser for metal sheet cutting applications. In 2010, after having spent eight years in Japan, Jean-François came back to Canada as a faculty member at the Department of Physics and Astronomy of Université de Moncton. Aside from teaching a variety of physics courses, he performs research works on lasers and nanostructured materials for laser applications. His most recent achievements include the realization of a solar-pumped laser without concentrator and a single-frequency laser based on exceptional points in the polarization space using anisotropic laser mirrors.
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